How long do you store fresh water in tank?

TNGW1500SE wrote:
How long do you store CITY fresh water in the fresh water tank before you get concerned?

I don't concern myself with that. I fill the tank in the spring and then throughout the season. when we're parked between trips I don't drain the tank. at the end of the season I drain and winterize. in your case drain and re-fill according to whatever schedule gives you peace of mind.